Materials Data on MnSi6Pb8O21 by Materials Project
MnPb8Si6O21 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Mn2+ is bonded to six equivalent O2- atoms to form distorted MnO6 pentagonal pyramids that share corners with six equivalent SiO4 tetrahedra and faces with two equivalent PbO6 octahedra. All Mn–O bond lengths are 2.25 Å. There are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.28–2.62 Å. In the second Pb2+ site, Pb2+ is bonded to six O2- atoms to form distorted PbO6 octahedra that share corners with six equivalent SiO4 tetrahedra and a faceface with one MnO6 pentagonal pyramid. There are three shorter (2.54 Å) and three longer (2.71 Å) Pb–O bond lengths. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent PbO6 octahedra, a cornercorner with one MnO6 pentagonal pyramid, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–69°. There are a spread of Si–O bond distances ranging from 1.64–1.68 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two Pb2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Mn2+, two Pb2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Pb2+ and one Si4+ atom.